1. Field of the Invention
This invention relates to syringe having a plunger guide that is adapted to stabilize the reciprocal movement of a plunger assembly and facilitate the manipulation of the syringe during fluid aspiration and injection steps completed by a health care worker and requiring the use of only one hand.
2. Background Art
Prior to the administration of an injection, the syringe that delivers the injection to a target tissue site is infused with fluid (e.g. medication) stored in a pharmaceutical vial by means of a needle cannula that penetrates the septum of the vial. A health care worker typically cradles the barrel of the syringe with one hand while using the other hand to retract the plunger assembly proximally through the barrel, whereby the complete the fluid aspiration step. The injection is then administered as the health care worker drives the plunger assembly distally through the barrel to expulse the fluid contents thereof into the target tissue site.
During the fluid aspiration step, it is common for the hand of the heath care worker which cradles the syringe barrel to also cover the usual calibration lines printed thereon, such that said lines are partially or totally obscured. Consequently, the syringe barrel may be overfilled with fluid from the pharmaceutical vial. What is more, the retraction of the piston assembly during the fluid aspiration step is frequently characterized by an unstable ride caused by the arm movement of the health care worker. The foregoing results in the inability of the health care worker to accurately infuse the syringe barrel with a precise volume of fluid from the vial and further contributes to overfilling the barrel. Accordingly, the excess fluid is often expulsed from the syringe barrel and discarded prior to the injection step. As will be appreciated by those skilled in the art, discarding the excess fluid can result in inefficiency and waste, particularly when the fluid is very expensive to manufacture and/or rare in availability.
It would therefore be desirable to have an aspirating syringe that can be reliably manipulated by a health care worker so that the syringe barrel will be accurately filled with a precise volume of fluid, whereby to eliminate the waste and inefficiency commonly associated with conventional syringes.